In box 20 (locality name), should I use what is listed on my W2, or use the code turbo tax says to use at the bottom of the screen?

You can enter what is shown on your Form W-2. In your case you would enter LNS since that is what your W-2 says. The TurboTax program will recognize LNS as Lansing as well. If for some reason the program is insisting that you use LAN, you can use it in that instance. Either way you should not experience an issue. We just recommend that you enter exactly what your W-2 says.